Add UMA histograms for WebUSB.

chrome/browser/usb/usb_chooser_bubble_delegate.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/usb/usb_chooser_bubble_delegate.h"
 
 #include <stddef.h>
 #include <utility>
 
 #include "base/bind.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/stl_util.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/usb/usb_chooser_context.h"
 #include "chrome/browser/usb/usb_chooser_context_factory.h"
 #include "components/bubble/bubble_controller.h"
 #include "content/public/browser/render_frame_host.h"
 #include "content/public/browser/web_contents.h"
 #include "device/core/device_client.h"
 #include "device/devices_app/usb/type_converters.h"
 #include "device/usb/usb_device.h"
 #include "device/usb/usb_device_filter.h"
 #include "url/gurl.h"
 
 namespace {
 
+enum WebUsbChooserClosed {
+  // The user cancelled the permission prompt without selecting a device.
+  WEBUSB_CHOOSER_CLOSED_CANCELLED = 0,
+  // The user probably cancelled the permission prompt without selecting a
+  // device because there were no devices to select.
+  WEBUSB_CHOOSER_CLOSED_CANCELLED_NO_DEVICES,
+  // The user granted permission to access a device.
+  WEBUSB_CHOOSER_CLOSED_PERMISSION_GRANTED,
+  // The user granted permission to access a device but that permission will be
+  // revoked when the device is disconnected.
+  WEBUSB_CHOOSER_CLOSED_EPHEMERAL_PERMISSION_GRANTED,
+  // Maximum value for the enum.
+  WEBUSB_CHOOSER_CLOSED_MAX
+};
+
 // Check if the origin is in the description set.
 bool FindOriginInDescriptorSet(const device::WebUsbDescriptorSet* set,
                                const GURL& origin) {
   if (!set)
     return false;
 
   if (ContainsValue(set->origins, origin))
     return true;
 
   for (const auto& config : set->configurations) {
@@ skipping 62 matching lines @@
       UsbChooserContextFactory::GetForProfile(profile);
   chooser_context->GrantDevicePermission(
       render_frame_host_->GetLastCommittedURL().GetOrigin(), embedding_origin,
       devices_[index].first->guid());
 
   device::usb::DeviceInfoPtr device_info_ptr =
       device::usb::DeviceInfo::From(*devices_[index].first);
   callback_.Run(std::move(device_info_ptr));
   callback_.reset();  // Reset |callback_| so that it is only run once.
 
+  if (devices_[index].first->serial_number().empty()) {
+    UMA_HISTOGRAM_ENUMERATION(
+        "WebUsb.ChooserClosed",
+        WEBUSB_CHOOSER_CLOSED_EPHEMERAL_PERMISSION_GRANTED,

[Alexei Svitkine (slow), 2016/01/18 20:05:13]

Nit: Each histogram macro expands to a lot of code. Can you make a helper
function for this that just takes the enum as a param?

[Reilly Grant (use Gerrit), 2016/01/20 00:59:37]

Done.

+        WEBUSB_CHOOSER_CLOSED_MAX);
+  } else {
+    UMA_HISTOGRAM_ENUMERATION("WebUsb.ChooserClosed",
+                              WEBUSB_CHOOSER_CLOSED_PERMISSION_GRANTED,
+                              WEBUSB_CHOOSER_CLOSED_MAX);
+  }
+
   if (bubble_controller_)
     bubble_controller_->CloseBubble(BUBBLE_CLOSE_ACCEPTED);
 }
 
 void UsbChooserBubbleDelegate::Cancel() {
+  if (devices_.size() == 0) {
+    UMA_HISTOGRAM_ENUMERATION("WebUsb.ChooserClosed",
+                              WEBUSB_CHOOSER_CLOSED_CANCELLED_NO_DEVICES,
+                              WEBUSB_CHOOSER_CLOSED_MAX);
+  } else {
+    UMA_HISTOGRAM_ENUMERATION("WebUsb.ChooserClosed",
+                              WEBUSB_CHOOSER_CLOSED_CANCELLED,
+                              WEBUSB_CHOOSER_CLOSED_MAX);
+  }
+
   if (bubble_controller_)
     bubble_controller_->CloseBubble(BUBBLE_CLOSE_CANCELED);
 }
 
 void UsbChooserBubbleDelegate::Close() {}
 
 void UsbChooserBubbleDelegate::OnDeviceAdded(
     scoped_refptr<device::UsbDevice> device) {
   if (device::UsbDeviceFilter::MatchesAny(device, filters_) &&
       FindOriginInDescriptorSet(
@@ skipping 31 matching lines @@
     }
   }
   if (observer())
     observer()->OnOptionsInitialized();
 }
 
 void UsbChooserBubbleDelegate::set_bubble_controller(
     BubbleReference bubble_controller) {
   bubble_controller_ = bubble_controller;
 }